By Kathleen Berger in collaboration with Washington University in St. Louis
Store shelves are stocked with products that promise to kill bacteria. Many people buy soaps or other items looking for the word ‘antibacterial’ on labels to protect themselves and their families from germs that make them sick. But new research at Washington University in St. Louis finds how a chemical that’s supposed to kill bacteria is actually making them stronger and more capable of surviving antibiotic treatment.
Triclosan is the active ingredient responsible for an antibacterial property marketed by companies. It’s been added to toothpaste, mouthwash, cosmetics and even to clothing, baby toys and credit cards with the intention of reducing or preventing bacterial growth.
In 2017, the U.S. Food and Drug Administration cited both safety concerns and lack of efficacy when it recommended against adding triclosan to consumer soaps. Since then, many companies replaced triclosan with other antibacterial active ingredients. But experts warn consumers to make sure triclosan isn’t in the products they buy, as not all companies were willing and the guidelines have not discouraged companies from adding it to other products.
Petra Levin, PhD, professor of biology at Washington University in St. Louis, explained how triclosan is very stable and lingers in the body and in the environment for a long time. Levin and Corey Westfall, a postdoctoral scholar in the Levin Lab, are not supporters of the antibacterial consumer push, regardless of the active ingredient. Both say hand washing with plain soap and water does the job, and the same goes for cleaning and wiping things down, encouraging regular soap, cleaning or bleach products- depending on the task.
“I think when it comes to anything antibacterial or antimicrobial should be left to doctors mainly,” said Westfall. “We should leave them out of consumer products.”
“At least in your day to day life, washing with antibacterial soap does not provide any advantage to cleaning your hands as to really lathering with soap and washing your hands with just plain soap that doesn’t have anything added in it,” said Levin.
It was Levin’s lab that did the work to figure out what’s really going on in the microbial world to see if and how triclosan interferes with antibiotic treatment.
“Triclosan increased the number of surviving bacterial cells substantially,” Levin said. “Normally, one in a million cells survive antibiotics, and a functioning immune system can control them. But triclosan was shifting the number of cells. Instead of only one in a million bacteria surviving, one in 10 organisms survived after 20 hours. Now, the immune system is overwhelmed.”
Triclosan exposure allowed the bacteria to escape death by antibiotics. And the protective property was not limited to any single family of antibiotics. In fact, multiple antibiotics that are considered unique in how they kill cells were less effective at killing bacteria exposed to triclosan.
Levin said the lab’s discoveries are every bit as alarming as they suspected. Triclosan exposure may inadvertently drive bacteria into a state in which they are able to tolerate normally lethal concentrations of antibiotics — including those antibiotics that are commonly used to treat urinary tract infections (UTIs).
The researchers tested antibiotics used to treat common urinary tract infections. The testing was conducted with mice. The study shows how triclosan limits the body’s ability to respond to antibiotic treatment.
All of the mice with the infection received Cipro to treat the UTI. Only some of the mice drank triclosan-spiked water. After antibiotic treatment, mice with triclosan exposure had a large number of bacteria in their urine and stuck to the bladder; mice without exposure had significantly lower bacterial counts.
“The magnitude of the difference in bacterial load between the mice that drank triclosan-spiked water and those that didn’t is striking,” Levin said.
“If the difference in the number of bacteria between the groups was less than tenfold, it would be difficult to make a strong case that the triclosan was the culprit,” Levin added. “We found 100 times more bacteria in the urine of triclosan-treated mice — that is a lot.”
In HEC’s video, Levin and Westfall explain in greater detail how bacteria are escaping death with Triclosan as the culprit.